This invention relates generally to fluid (liquid or gas) mixture monitoring method and apparatus. More particularly, it concerns the use of a bidirectional microwave transmitter/receiver to interrogate a conduit through which may be passed a heterogeneous fluid mixture the constituents of which are dielectrically distinct, thereby to determine the ratio of the two fluid mixture constituents within the conduit. The method and apparatus of the invention are described in the context of pumping water to retrieve crude oil from the ground and monitoring at the oil wellhead the volumetric ratio of oil to water in the oil/water fluid mixture flowing thereat. This is a current commercial application with respect to which the invention has particular utility. The invention is also believed to be useful in the protection of the environment and in energy conservation, e.g. by detecting oil pipeline leakage that might contaminate groundwater and waste fossil fuel.
Water is often used to pump crude oil from the ground. On oil-lease land, a landowner earns royalties based roughly upon the oil yielded from the leased land. Heretofore, such royalty calculations have been imprecise, resulting in inaccurate accountings of royalties to landowners. While it has been possible to monitor the mixed oil/fluid volume at each oil wellhead, it has not been possible to monitor the percentage of that volume which is oil, rather than water. Oil and water have different densities and fluid tendencies, but their generally heterogeneous mixture within oil pipelines have made it impossible to perform in-line monitoring of their respective volumes.
As disclosed in my U.S. Pat. No. 4,234,844, issued Nov. 18, 1980, entitled "Electromagnetic Noncontacting Measuring Apparatus", it is possible to monitor electrical conditions by generating and focusing electromagnetic energy at a pair of electrically related, spaced focal points. An important application of such electrical condition monitoring is described in my companion U.S. Pat. No. 4,912,982 issued Apr. 3, 1990, whereby certain fluid parameters such as the rate of flow of a homogeneous fluid through a conduit can be measured. Such flow rate monitoring depends upon the monitoring of the dielectric constant within an interrogation zone, as is described in my companion U.S. Pat. No. 4,947,848, issued Aug. 14, 1990. These patent disclosures are incorporated herein by this reference.
It is a principal object of the invention to provide method and apparatus for monitoring the dielectric constant within an interrogation region embracing a fluid conduit through which passes a heterogeneous mixture of two fluid constituents having disparate dielectric constants to produce a measure of the relative volume of each constituent in the mixture.
Another object is to provide such method and apparatus that can be used to monitor the volumetric ratio, for example, of the constituents of a crude oil/water mixture.
Yet another object is to provide such monitoring compatibly with existing oil wellhead fixtures, and adaptably to future field requirements and standards.
It is still another object to provide such monitoring method and apparatus in real time and with negligent impact on oil wellhead output.
It is also an object to provide high-accuracy monitoring over a wide range of volumetric ratios between constituents.